Hello :
<span>4x-5y=13...(1)
x+5y=-3...(2)
(1)+(2) : 5x = 10
x=2
subsct in (2) : 2+5y = -3
5y =-5
y = -1
</span>
Step 1. Identify the unit you have
Step 2. Identify the unit you want to covert to
Step 3. Count the number of units between them
(<span>If </span>you<span> are going from a larger </span>unit<span> to a smaller </span>unit<span>, </span>you<span> multiply by 10 successively.)</span>
300 is the original amount and 0.5 is the rate (a percent) which is deacying because it is less than 1